Adults often seek orthodontic treatment to correct a misaligned bite or jaw profile. Unlike children, an adult’s jaw structures are fully developed and fixed. While adult jaw structures cannot be moved on the scale seen during growth, adult orthodontics is highly effective for improving function and aesthetics. The fixed nature of the jawbones means the approach to achieving alignment must be modified compared to adolescent treatment.
Understanding Tooth Movement Versus Jaw Correction in Adults
The fundamental difference between treating adults and adolescents lies in the maturity of the skeletal structure. By adulthood, the maxilla (upper jaw) and mandible (lower jaw) have completed their growth and are permanently fused. This makes significant structural repositioning impossible with braces alone. Orthodontic appliances work by moving the teeth within the existing jawbone, not by remodeling the jaw itself.
This movement is possible due to the periodontal ligament (PDL), a thin layer of connective tissue that surrounds the tooth root and anchors it to the alveolar bone. When a consistent, gentle force is applied by an orthodontic appliance, the PDL signals a biological process of bone remodeling. Cells called osteoclasts break down the bone on the side of pressure, while osteoblasts rebuild bone on the side of tension, allowing the tooth to slowly shift position.
This mechanism allows for precise dental changes, but it cannot override a major skeletal mismatch. For mild jaw discrepancies, orthodontists use “dental compensation.” This involves moving the teeth to camouflage the skeletal issue, such as tilting the front teeth inward or outward to meet correctly. This technique creates the appearance of a proper bite, achieving a functional and aesthetically pleasing result by adjusting the teeth to fit the existing jaw relationship.
Jaw Alignment Issues Amenable to Braces Alone
Braces and aligners successfully correct malocclusions that are primarily dental or involve only a mild skeletal discrepancy. Common issues like dental crowding, where there is insufficient space, are managed effectively. Mild overbites (Class II) or underbites (Class III) due primarily to tooth position, rather than severe jaw size differences, are also treatable non-surgically. Minor crossbites, where a few teeth are positioned incorrectly relative to their opposing teeth, can typically be resolved by repositioning the individual teeth.
To create the necessary space for alignment, two main non-surgical techniques are used.
Interproximal Reduction (IPR)
Interproximal reduction (IPR), also called enamel stripping, involves the careful removal of a small amount of outer enamel from the sides of teeth. This procedure is reserved for cases of mild to moderate crowding, often yielding a few millimeters of space across the arch. IPR is also used to correct minor discrepancies in tooth size between the upper and lower arches, ensuring a better final bite.
Tooth Extraction
In cases of more severe crowding or significant dental protrusion, the orthodontist may recommend the extraction of one or more permanent teeth, often premolars. The space created allows the remaining teeth to be retracted, correcting the crowding and leveling the bite. This strategic removal is a key tool in achieving dental compensation and a stable, aligned bite without altering the jawbones.
The Necessity of Combined Orthodontic and Surgical Treatment
When misalignment is severe and the jawbones are significantly mismatched in size or position, braces alone are insufficient for a functional or stable outcome. Severe skeletal discrepancies, such as a pronounced overbite or underbite, require a definitive change to the jaw structure itself. Treatment involves collaboration between the orthodontist and an oral and maxillofacial surgeon in a process called combined orthodontic and orthognathic surgery.
Orthognathic surgery physically repositions the maxilla, mandible, or both, moving the jawbones into a more balanced and functional relationship. This major procedure is required because the dense, mature bone of the adult jaw cannot be substantially moved by orthodontic forces alone. The entire process is divided into distinct phases, beginning with pre-surgical orthodontics.
The purpose of this initial orthodontic phase is to “decompensate” the teeth. This means the teeth are moved into the positions they should occupy over their respective jawbones, which often temporarily makes the bite look worse. This decompensation eliminates the dental camouflage the teeth adopted to mask the underlying jaw problem, allowing the surgeon to see the true skeletal discrepancy. Once the teeth are correctly aligned, surgery moves the jawbones so the teeth meet properly. The final phase, post-surgical orthodontics, involves a refinement period lasting five to eleven months to perfect the final bite and ensure long-term stability.